Thermally treated Korean ilmenite was characterized and used for water splitting to obtain hydrogen by photo-catalytic reaction. Experiments on specific surface area, X-ray diffraction and EDS showed that the formation of FeO, $Fe_2O_3$ and $TiO_2$ ilmenite crystal surface increased the specific surface area with maximum value, phase change of $TiO_2$ at $600^{circ}C$ and hetrogeneity. The hydrogen evolved in caustic soda solution on these ilmenites indicated that there was a maximum yield point at about $600^{circ}C$. This point was explained with the change of the surface area due to sintering of newly formed FeO, $Fe_2O_3$ and $TiO_2$, as well as crystal phase change of anatase to rutile at $600^{circ}C$. Produced hydrogen increased also as the concentration of caustic soda, but become constant at the near 1N solution.